This invention relates to ink jet printing systems and, more particularly, to a new and improved ink jet printer having a printhead capable of ink jet printing in different orientations and relative positions.
Ink jet printing systems include a printhead having small orifices through which ink is ejected in a controlled manner to form an image on an adjacent substrate. To counteract the effect of capillary action in the small orifices which would otherwise cause ink to seep out of the printhead when not in use but, at the same time, prevent air from being drawn into the printhead through the orifices, the ink in the printhead must be maintained at a selected negative pressure which is dependent upon the orifice size and the ink characteristics and may be, for example, about 2 to 3 inches of water. In ink jet printing systems having a remote ink supply connected to the printhead through a supply line, however, the pressure of the ink in the printhead can be affected by the relative vertical positions of the printhead and the remote ink supply. Moreover, many ink jet printers are designed to operate only in one orientation of the printhead, which limits the manner in which the ink jet system can be used.
In ink jet printing systems using hot melt ink, which is solid at room temperature and becomes liquid at elevated temperatures, the ink is ejected from the printhead at a relatively high temperature which is sufficient to ensure low enough viscosity of the ink for the desired operation. Such hot melt inks, however, tend to deteriorate when maintained at high temperature, which tends to limit the usefulness of hot melt ink jet printing systems.